Some surgical procedures require the tissue to be transected and closed. This is often the case in gastrointestinal tract surgery when a tumor or injury to the tract occurs. Typically transections are made both proximally and distally on opposite sides of the tumor or injured section. For example, a cancerous tumor located on a patient's colon may be removed by transecting the colon on the proximal side of the tumor and then a second transectoin on the distal side of the tumor. Thus, the anomalous tissue section may be removed while leaving two remnant limbs of the colon, which are subsequently anastomosed or rejoined. Since exposing the surrounding tissues to the interior contents of the colon or other organ may greatly increase the risk of infection and associated complications, it is desirable for the remnant limbs to remain closed until the limbs are anastomosed or rejoined.
A linear cutter is a surgical device that clamps tissue, typically between two opposed jaws, and staples and cuts the clamped tissue. Some arrangements include a stapling mechanism, which drives rows of staples into the tissue, typically before or simultaneous to the cutting. These rows of staples serve to transect and close the open ends of the cut organ, thereby limiting any exposure of surrounding tissue to the contents of the organ. Advantageously one or more rows of staples are driven on each side of each cut.
In the stapling procedures described above, staples are typically driven with a staple pusher disposed in one of the clamping jaws. The staple pusher forms the staples by pressing the staples from the first clamping jaw, into and through the clamped tissue, and into an anvil in the opposed clamping jaw configured to bend or otherwise form the staple closure. In order to effectively staple the tissue, it is advantageous to clamp the tissue such that a small thickness, e.g., one millimeter, is disposed between the two clamping jaws. To achieve this result, the clamping jaws must exert and maintain a substantial amount of clamping force. A difficulty may then arise when the staples are driven into the clamped tissue, since the driving of the staples from one of the jaws into an anvil in the other of the jaws applies a force between the jaws that is opposite the clamping force. Thus, during the stapling, even greater clamping force is required to be exerted by the clamping jaws. That is, the clamping jaws must apply sufficient force to both maintain the desired tissue gap between the jaws and to form the staples into their fastened configuration. High clamping forces can be problematic in that the proximally supported jaws may deflect or splay outwardly, thereby making it difficult to achieve a uniform tissue gap along the length of the jaws.
U.S. Pat. No. 4,520,817 discloses a mechanism to potentially alleviate the aforementioned problems by providing a block carrying the staple pusher and cutter with a plurality of lateral projections that ride in slots in the opposed jaws as the cutter and pusher are moved distally. These projection/slot engagements may assist with maintaining a clamping force by providing local support between the jaws in the region of the staple pusher. However, a substantial amount of distally directed force must be applied to the stapler pusher in order to simultaneously cut the tissue, press and form the staples, and overcome the additional resistance due to the projection/slot arrangement. Since the device of U.S. Pat. No. 4,520,817 is a handheld unit requiring full access to the surgical site, the operator is able to manually apply the substantial force, by pushing a knob, at a location that is very close to the jaws.
Some of the aforementioned procedures may be performed endoscopically, which is generally less invasive and allows for more rapid healing as compared to open surgery, which may require large incisions to allow for the access required to utilize manual surgical instruments. Endoscopic procedures typically entail insertion of instruments through a small incision point, e.g., through a cannula. The surgical tools required to perform these procedures generally have elongated shafts that extend from a handpiece or other base unit to an end effector.
The end effectors of endoscopic surgical instruments are commonly referred to as the “business end” of the instrument. They contain components such as fasteners, which are often in the form of surgical staples. These end effectors may transect, form anastomoses in, and occlude viscera and vessels in the human body.
Since the end effector and shaft have relatively small diameters, the end effector and shaft may be inserted through the cannula to perform the procedure while the operator controls the instrument from outside the surgical site. A drawback of such devices is that they generally require the transfer of mechanical force generated manually by the operator from the handpiece or base to the end effector. This is accomplished by drive shafts, pushrods, cables, and the like extending through the shaft. The transfer of power through these mechanisms results in substantial power losses and makes precise control extremely difficult. Further, these drawbacks may be amplified in systems that utilize flexible shafts.
Due to the mechanical inefficiencies of these endoscopic instruments, the projection/slot arrangement of U.S. Pat. No. 4,520,817, which requires a substantial amount of distally applied manual force to drive the staple pusher and cutter, is not well suited for endoscopic end effectors. U.S. Pat. No. 4,520,817 discloses a handheld unit requiring full access to the surgical site, whereby the operator is able to apply the substantial force, by pushing a knob, at a location that is very close to the jaws. This is not feasible for endoscopic or natural orifice procedures which are inherently superior procedures to open and/or endoscopic procedures due to minimized patient trauma and operating room time.
Thus, there is a need for devices and methods that provide an improved power transmission to the end effector. Further there is a need for devices and methods that provide improved clamping in an end effector.
Further, for surgical instruments where an end effector is attached to a flexible shaft, there is known a difficulty in effectively transferring force to the end effector via the flexible shaft. In this regard, an effective flexible stapler would allow surgeons to utilize natural orifices or an umbilical approach to surgery. An effective flexible shafted stapler would allow advances in surgery through a single port approach which would lead to a reduction in pain, elimination of incisions, and reduced operating room time for the patient.
Further, many surgical staplers utilize actuation mechanisms that utilize a drive band which is most often manually operated. These manually operated devices require an operator to manually pull a lever to either provide a one-to-one stroke or to manually repeatedly pull a trigger to achieve a desired actuation. Such devices rely on the force applied by the operator (e.g., a force between the operator's fingers and thumb) for actuation. In this regard, there is a need for a device that does not require a drive band and is powered by means other than manual manipulation.